Re: simple question

Hint: If you have a ratio of 1/25000, then going from map scale to real scale means you multiply by the inverse ration which is 1/(1/25000) = 25000. So 25000x10cm = 250000cm = 2500m = 2.5km.

Its always the case that if you have a ratio to go from one unit to another (in this case some form of metres to map units) then going in the reverse (map units to some form of metres) is done by calculating the reciprocal of the ratio.

Re: simple question

I would like to add that we may also consider unitary method for better understanding.
from the scale 1/25000 what is given is
1 cm on scale represents 25000 cm on ground, this part must be well understood. Now it becomes quite simlple
10 cm on scale will represent 10 * 25000 cm = 250000 cm = 250000/100000= 2.5 km
In case we are given that two places on ground are 15 km away what will be the distance between them on the map.
We proceed exactly is the same manner. What is to be found / calculate must be kept on the right side that is at the end.
25000 cm on ground will be 1 cm away from each other on map. 25000 cm = 25000/100000= 0.25 km
So we have25000 cm on ground = 1 cm on map
1 cm on ground = 1/25000 cm on map
100000 cm= 1km on ground = 100000/25000 cm = 4 cm on map
15 km on ground = 15*4 = 60 cm on map